From 95877580d6a69738d42e770dffd774257cb6118f Mon Sep 17 00:00:00 2001
From: Onur Gumus <onur@outlook.com.tr>
Date: Wed, 1 Apr 2026 12:20:26 +0200
Subject: [PATCH 1/8] [All] Add support for Guid.CreateVersion7() and
 Guid.CreateVersion7(DateTimeOffset)

Implement RFC 9562 UUID v7 generation across all targets (JS/TS, Python,
Rust, Dart, Beam) with both parameterless and DateTimeOffset overloads.
---
 src/Fable.Cli/CHANGELOG.md                  |  4 +++
 src/Fable.Compiler/CHANGELOG.md             |  4 +++
 src/Fable.Transforms/Beam/Replacements.fs   |  4 +++
 src/Fable.Transforms/Dart/Replacements.fs   |  6 ++++
 src/Fable.Transforms/Python/Replacements.fs |  6 ++++
 src/Fable.Transforms/Replacements.fs        |  6 ++++
 src/Fable.Transforms/Rust/Replacements.fs   |  4 +++
 src/fable-library-beam/fable_guid.erl       | 36 ++++++++++++++++++++-
 src/fable-library-py/fable_library/guid.py  | 32 ++++++++++++++++++
 src/fable-library-rust/Cargo.toml           |  4 +--
 src/fable-library-rust/src/Guid.rs          | 12 +++++++
 src/fable-library-ts/Guid.ts                | 22 +++++++++++++
 tests/Beam/GuidTests.fs                     | 21 ++++++++++++
 tests/Js/Main/TypeTests.fs                  | 21 ++++++++++++
 tests/Python/TestGuid.fs                    | 21 ++++++++++++
 tests/Rust/tests/src/GuidTests.fs           | 11 +++++++
 16 files changed, 211 insertions(+), 3 deletions(-)

diff --git a/src/Fable.Cli/CHANGELOG.md b/src/Fable.Cli/CHANGELOG.md
index cdc2dd1683..0748f399aa 100644
--- a/src/Fable.Cli/CHANGELOG.md
+++ b/src/Fable.Cli/CHANGELOG.md
@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Unreleased
 
+### Added
+
+* [All] Add support for `Guid.CreateVersion7()` and `Guid.CreateVersion7(DateTimeOffset)`
+
 ## 5.0.0-rc.6 - 2026-03-31
 
 ### Fixed
diff --git a/src/Fable.Compiler/CHANGELOG.md b/src/Fable.Compiler/CHANGELOG.md
index 045c355c7f..e916128cd5 100644
--- a/src/Fable.Compiler/CHANGELOG.md
+++ b/src/Fable.Compiler/CHANGELOG.md
@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Unreleased
 
+### Added
+
+* [All] Add support for `Guid.CreateVersion7()` and `Guid.CreateVersion7(DateTimeOffset)`
+
 ## 5.0.0-rc.12 - 2026-03-31
 
 ### Fixed
diff --git a/src/Fable.Transforms/Beam/Replacements.fs b/src/Fable.Transforms/Beam/Replacements.fs
index 318675cf8a..7e08dc1891 100644
--- a/src/Fable.Transforms/Beam/Replacements.fs
+++ b/src/Fable.Transforms/Beam/Replacements.fs
@@ -3855,6 +3855,10 @@ let private guids
             Helper.LibCall(com, "fable_guid", "from_bytes", t, [ arg ], ?loc = r) |> Some
         | _ -> None
     | "NewGuid" -> Helper.LibCall(com, "fable_guid", "new_guid", t, [], ?loc = r) |> Some
+    | "CreateVersion7" ->
+        match args with
+        | [] -> Helper.LibCall(com, "fable_guid", "create_version7", t, [], ?loc = r) |> Some
+        | _ -> Helper.LibCall(com, "fable_guid", "create_version7", t, args, ?loc = r) |> Some
     | "Parse" ->
         match args with
         | [ StringConst literalGuid ] ->
diff --git a/src/Fable.Transforms/Dart/Replacements.fs b/src/Fable.Transforms/Dart/Replacements.fs
index ae56c31014..9a8448239d 100644
--- a/src/Fable.Transforms/Dart/Replacements.fs
+++ b/src/Fable.Transforms/Dart/Replacements.fs
@@ -3450,6 +3450,12 @@ let guids
 
     match i.CompiledName with
     | "NewGuid" -> Helper.LibCall(com, "Guid", "newGuid", t, []) |> Some
+    | "CreateVersion7" ->
+        match args with
+        | [] -> Helper.LibCall(com, "Guid", "createVersion7", t, []) |> Some
+        | _ ->
+            Helper.LibCall(com, "Guid", "createVersion7", t, args, i.SignatureArgTypes)
+            |> Some
     | "Parse" ->
         match args with
         | [ StringConst literalGuid ] -> parseGuid literalGuid
diff --git a/src/Fable.Transforms/Python/Replacements.fs b/src/Fable.Transforms/Python/Replacements.fs
index ce8f64fb6d..a1364a51b2 100644
--- a/src/Fable.Transforms/Python/Replacements.fs
+++ b/src/Fable.Transforms/Python/Replacements.fs
@@ -3478,6 +3478,12 @@ let guids
     =
     match i.CompiledName with
     | "NewGuid" -> Helper.LibCall(com, "guid", "new_guid", t, []) |> Some
+    | "CreateVersion7" ->
+        match args with
+        | [] -> Helper.LibCall(com, "guid", "create_version7", t, []) |> Some
+        | _ ->
+            Helper.LibCall(com, "guid", "create_version7", t, args, i.SignatureArgTypes)
+            |> Some
     | "Parse" -> Helper.LibCall(com, "guid", "parse", t, args, i.SignatureArgTypes) |> Some
     | "TryParse" -> Helper.LibCall(com, "guid", "try_parse", t, args, i.SignatureArgTypes) |> Some
     | "ToByteArray" ->
diff --git a/src/Fable.Transforms/Replacements.fs b/src/Fable.Transforms/Replacements.fs
index d6a69464ed..55fb9aa4f8 100644
--- a/src/Fable.Transforms/Replacements.fs
+++ b/src/Fable.Transforms/Replacements.fs
@@ -3822,6 +3822,12 @@ let guids
 
     match i.CompiledName with
     | "NewGuid" -> Helper.LibCall(com, "Guid", "newGuid", t, []) |> Some
+    | "CreateVersion7" ->
+        match args with
+        | [] -> Helper.LibCall(com, "Guid", "createVersion7", t, []) |> Some
+        | _ ->
+            Helper.LibCall(com, "Guid", "createVersion7", t, args, i.SignatureArgTypes)
+            |> Some
     | "Parse" ->
         match args with
         | [ StringConst literalGuid ] -> parseGuid literalGuid
diff --git a/src/Fable.Transforms/Rust/Replacements.fs b/src/Fable.Transforms/Rust/Replacements.fs
index 861aeb0763..377d1e9c34 100644
--- a/src/Fable.Transforms/Rust/Replacements.fs
+++ b/src/Fable.Transforms/Rust/Replacements.fs
@@ -3121,6 +3121,10 @@ let guids
         | _ -> None
     // | "Empty", None, [] -> // it's a static field, see tryField
     | "NewGuid", None, [] -> Helper.LibCall(com, "Guid", "new_guid", t, args, ?loc = r) |> Some
+    | "CreateVersion7", None, [] -> Helper.LibCall(com, "Guid", "create_version7", t, [], ?loc = r) |> Some
+    | "CreateVersion7", None, _ ->
+        Helper.LibCall(com, "Guid", "create_version7_with_timestamp", t, args, ?loc = r)
+        |> Some
     | "Parse", None, [ ExprType String ] -> Helper.LibCall(com, "Guid", "parse", t, args, ?loc = r) |> Some
     | "TryParse", None, [ ExprType String; _ ] -> Helper.LibCall(com, "Guid", "tryParse", t, args, ?loc = r) |> Some
     | "ToByteArray", Some x, [] -> Helper.LibCall(com, "Guid", "toByteArray", t, [ x ], ?loc = r) |> Some
diff --git a/src/fable-library-beam/fable_guid.erl b/src/fable-library-beam/fable_guid.erl
index a9ba857b70..074435f75d 100644
--- a/src/fable-library-beam/fable_guid.erl
+++ b/src/fable-library-beam/fable_guid.erl
@@ -1,9 +1,12 @@
 -module(fable_guid).
 -export([
-    new_guid/0, parse/1, try_parse/1, try_parse/2, from_bytes/1, to_byte_array/1, to_string_format/2
+    new_guid/0, create_version7/0, create_version7/1,
+    parse/1, try_parse/1, try_parse/2, from_bytes/1, to_byte_array/1, to_string_format/2
 ]).
 
 -spec new_guid() -> binary().
+-spec create_version7() -> binary().
+-spec create_version7(integer()) -> binary().
 -spec parse(binary()) -> binary().
 -spec try_parse(binary()) -> {boolean(), binary()}.
 -spec try_parse(binary(), reference()) -> boolean().
@@ -26,6 +29,37 @@ new_guid() ->
         )
     ).
 
+%% Generate a new UUID v7 (RFC 9562) with current timestamp.
+create_version7() ->
+    Ms = erlang:system_time(millisecond),
+    create_version7(Ms).
+
+%% Generate a new UUID v7 (RFC 9562) with given DateTimeOffset or ms since Unix epoch.
+create_version7({Ticks, _Kind, _Offset}) ->
+    %% DateTimeOffset tuple: convert .NET ticks to Unix epoch milliseconds
+    %% .NET ticks are 100ns intervals since 0001-01-01
+    %% Unix epoch in .NET ticks = 621355968000000000
+    Ms = (Ticks - 621355968000000000) div 10000,
+    create_version7(Ms);
+create_version7(Timestamp) when is_integer(Timestamp) ->
+    <<RandA0:16, RandB0:64>> = crypto:strong_rand_bytes(10),
+    RandA = RandA0 band 16#0FFF,
+    RandB = RandB0 band 16#3FFFFFFFFFFFFFFF,
+    %% 48-bit timestamp split into A (high 32 bits) and B (low 16 bits)
+    A = (Timestamp bsr 16) band 16#FFFFFFFF,
+    B = Timestamp band 16#FFFF,
+    %% Version 7: top 4 bits = 0111
+    C = 16#7000 bor RandA,
+    %% Variant: top 2 bits = 10
+    D = 16#8000 bor ((RandB bsr 48) band 16#3FFF),
+    E = RandB band 16#FFFFFFFFFFFF,
+    list_to_binary(
+        io_lib:format(
+            "~8.16.0b-~4.16.0b-~4.16.0b-~4.16.0b-~12.16.0b",
+            [A, B, C, D, E]
+        )
+    ).
+
 %% Construct a GUID from a 16-byte array (binary or list of integers).
 %% .NET uses mixed-endian: first 3 groups are little-endian, last 2 are big-endian.
 from_bytes({byte_array, _, _} = BA) ->
diff --git a/src/fable-library-py/fable_library/guid.py b/src/fable-library-py/fable_library/guid.py
index b1a291fe83..ffe1c95605 100644
--- a/src/fable-library-py/fable_library/guid.py
+++ b/src/fable-library-py/fable_library/guid.py
@@ -1,3 +1,5 @@
+import os
+import time
 import uuid
 
 from .array_ import Array
@@ -32,8 +34,38 @@ def array_to_guid(guid: Array[byte]) -> uuid.UUID:
     return uuid.UUID(bytes_le=bytes(guid))
 
 
+def create_version7(timestamp: object | None = None) -> uuid.UUID:
+    """Create a UUID v7 per RFC 9562."""
+    if timestamp is None:
+        ms = int(time.time() * 1000)
+    else:
+        # DateTimeOffset has getTime() returning ms since epoch
+        ms = int(timestamp.getTime())  # type: ignore
+
+    # Build 16 bytes per RFC 9562
+    rand_bytes = os.urandom(10)
+
+    # Bytes 0-5: 48-bit big-endian ms timestamp
+    ts_bytes = ms.to_bytes(6, byteorder="big")
+
+    # Bytes 6-7: version (0111) + 12 bits rand_a
+    rand_a = int.from_bytes(rand_bytes[0:2], "big")
+    ver_rand_a = (0x7000 | (rand_a & 0x0FFF)).to_bytes(2, "big")
+
+    # Bytes 8-9: variant (10) + 14 bits rand_b
+    rand_b_hi = int.from_bytes(rand_bytes[2:4], "big")
+    var_rand_b = (0x8000 | (rand_b_hi & 0x3FFF)).to_bytes(2, "big")
+
+    # Bytes 10-15: 48 bits rand_b continued
+    rand_rest = rand_bytes[4:10]
+
+    all_bytes = ts_bytes + ver_rand_a + var_rand_b + rand_rest
+    return uuid.UUID(bytes=bytes(all_bytes))
+
+
 __all__ = [
     "array_to_guid",
+    "create_version7",
     "guid_to_array",
     "new_guid",
     "parse",
diff --git a/src/fable-library-rust/Cargo.toml b/src/fable-library-rust/Cargo.toml
index 093e229017..1f738b2508 100644
--- a/src/fable-library-rust/Cargo.toml
+++ b/src/fable-library-rust/Cargo.toml
@@ -31,7 +31,7 @@ rust_decimal = { version = "1.40", features = ["maths"], default-features = fals
 startup = { version = "0.1", path = "vendored/startup", optional = true }
 
 [target.'cfg(not(target_arch = "wasm32"))'.dependencies]
-uuid = { version = "1.22", features = ["v4"], default-features = false, optional = true }
+uuid = { version = "1.22", features = ["v4", "v7"], default-features = false, optional = true }
 
 [target.'cfg(target_arch = "wasm32")'.dependencies]
-uuid = { version = "1.22", features = ["v4", "js"], default-features = false, optional = true }
+uuid = { version = "1.22", features = ["v4", "v7", "js"], default-features = false, optional = true }
diff --git a/src/fable-library-rust/src/Guid.rs b/src/fable-library-rust/src/Guid.rs
index b7da890424..eca1af0547 100644
--- a/src/fable-library-rust/src/Guid.rs
+++ b/src/fable-library-rust/src/Guid.rs
@@ -52,4 +52,16 @@ pub mod Guid_ {
     pub fn toByteArray(x: Guid) -> Array<u8> {
         new_array(&x.0.to_bytes_le())
     }
+
+    pub fn create_version7() -> Guid {
+        Guid(Uuid::now_v7())
+    }
+
+    pub fn create_version7_with_timestamp(dto: crate::DateTimeOffset_::DateTimeOffset) -> Guid {
+        let millis = dto.toUnixTimeMilliseconds();
+        let secs = (millis / 1000) as u64;
+        let nanos = ((millis % 1000) * 1_000_000) as u32;
+        let ts = uuid::Timestamp::from_unix(uuid::NoContext, secs, nanos);
+        Guid(Uuid::new_v7(ts))
+    }
 }
diff --git a/src/fable-library-ts/Guid.ts b/src/fable-library-ts/Guid.ts
index b9a9ff2cd7..5bf7f31e78 100644
--- a/src/fable-library-ts/Guid.ts
+++ b/src/fable-library-ts/Guid.ts
@@ -74,6 +74,28 @@ export function newGuid() {
   return b;
 }
 
+// RFC 9562 UUID v7
+export function createVersion7(timestamp?: Date): string {
+  const ms = timestamp != null ? timestamp.getTime() : Date.now();
+
+  // 48-bit timestamp as hex
+  const msHex = Math.floor(ms).toString(16).padStart(12, "0");
+
+  // random bits
+  const randA = Math.floor(Math.random() * 0x1000); // 12 bits
+  const randB1 = Math.floor(Math.random() * 0x4000); // 14 bits
+  const randB2 = Math.floor(Math.random() * 0x100000000); // 32 bits
+  const randB3 = Math.floor(Math.random() * 0x10000); // 16 bits
+
+  const timeLow = msHex.slice(0, 8);
+  const timeMid = msHex.slice(8, 12);
+  const ver = (0x7000 | randA).toString(16).padStart(4, "0");
+  const variantAndRandB = (0x8000 | randB1).toString(16).padStart(4, "0");
+  const node = randB2.toString(16).padStart(8, "0") + randB3.toString(16).padStart(4, "0");
+
+  return `${timeLow}-${timeMid}-${ver}-${variantAndRandB}-${node}`;
+}
+
 // Maps for number <-> hex string conversion
 let _convertMapsInitialized = false;
 let _byteToHex: string[];
diff --git a/tests/Beam/GuidTests.fs b/tests/Beam/GuidTests.fs
index c65a67317f..f0eccab334 100644
--- a/tests/Beam/GuidTests.fs
+++ b/tests/Beam/GuidTests.fs
@@ -21,6 +21,27 @@ let ``test Guid.NewGuid creates different guids`` () =
     let g2 = Guid.NewGuid()
     g = g2 |> equal false
 
+[<Fact>]
+let ``test Guid.CreateVersion7 works`` () =
+    let g1 = Guid.CreateVersion7()
+    let g2 = Guid.CreateVersion7()
+    g1 = g2 |> equal false
+    let s1 = string g1
+    equal 36 s1.Length
+    equal '7' s1.[14]
+    let variantChar = s1.[19]
+    (variantChar = '8' || variantChar = '9' || variantChar = 'a' || variantChar = 'b') |> equal true
+
+[<Fact>]
+let ``test Guid.CreateVersion7 with DateTimeOffset works`` () =
+    let dto = DateTimeOffset(2024, 1, 1, 0, 0, 0, TimeSpan.Zero)
+    let g1 = Guid.CreateVersion7(dto)
+    let s1 = string g1
+    equal 36 s1.Length
+    equal '7' s1.[14]
+    let variantChar = s1.[19]
+    (variantChar = '8' || variantChar = '9' || variantChar = 'a' || variantChar = 'b') |> equal true
+
 [<Fact>]
 let ``test Guid equality works`` () =
     let s = "f46d24f0-183e-4fca-9f47-e382afdfde8b"
diff --git a/tests/Js/Main/TypeTests.fs b/tests/Js/Main/TypeTests.fs
index c97a5e73f4..2435ef4534 100644
--- a/tests/Js/Main/TypeTests.fs
+++ b/tests/Js/Main/TypeTests.fs
@@ -1119,6 +1119,27 @@ let tests =
         let g3 = Guid.Parse s1
         g1 = g3 |> equal true
 
+    testCase "Guid.CreateVersion7 works" <| fun () ->
+        let g1 = Guid.CreateVersion7()
+        let g2 = Guid.CreateVersion7()
+        g1 = g2 |> equal false
+        let s1 = string g1
+        equal 36 s1.Length
+        // Check version nibble is '7'
+        equal '7' s1.[14]
+        // Check variant nibble is 8, 9, a, or b
+        let variantChar = s1.[19]
+        (variantChar = '8' || variantChar = '9' || variantChar = 'a' || variantChar = 'b') |> equal true
+
+    testCase "Guid.CreateVersion7 with DateTimeOffset works" <| fun () ->
+        let dto = DateTimeOffset(2024, 1, 1, 0, 0, 0, TimeSpan.Zero)
+        let g1 = Guid.CreateVersion7(dto)
+        let s1 = string g1
+        equal 36 s1.Length
+        equal '7' s1.[14]
+        let variantChar = s1.[19]
+        (variantChar = '8' || variantChar = '9' || variantChar = 'a' || variantChar = 'b') |> equal true
+
     testCase "Guid.Empty works" <| fun () ->
         let g1 = Guid.Empty
         string g1 |> equal "00000000-0000-0000-0000-000000000000"
diff --git a/tests/Python/TestGuid.fs b/tests/Python/TestGuid.fs
index 7505d68d71..bb5cc843a3 100644
--- a/tests/Python/TestGuid.fs
+++ b/tests/Python/TestGuid.fs
@@ -21,6 +21,27 @@ let ``test Guid.NewGuid creates different guids`` () =
     let g2 = Guid.NewGuid()
     g = g2 |> equal false
 
+[<Fact>]
+let ``test Guid.CreateVersion7 works`` () =
+    let g1 = Guid.CreateVersion7()
+    let g2 = Guid.CreateVersion7()
+    g1 = g2 |> equal false
+    let s1 = string g1
+    equal 36 s1.Length
+    equal '7' s1.[14]
+    let variantChar = s1.[19]
+    (variantChar = '8' || variantChar = '9' || variantChar = 'a' || variantChar = 'b') |> equal true
+
+[<Fact>]
+let ``test Guid.CreateVersion7 with DateTimeOffset works`` () =
+    let dto = DateTimeOffset(2024, 1, 1, 0, 0, 0, TimeSpan.Zero)
+    let g1 = Guid.CreateVersion7(dto)
+    let s1 = string g1
+    equal 36 s1.Length
+    equal '7' s1.[14]
+    let variantChar = s1.[19]
+    (variantChar = '8' || variantChar = '9' || variantChar = 'a' || variantChar = 'b') |> equal true
+
 [<Fact>]
 let ``test Guid equality works`` () =
     let s = "f46d24f0-183e-4fca-9f47-e382afdfde8b"
diff --git a/tests/Rust/tests/src/GuidTests.fs b/tests/Rust/tests/src/GuidTests.fs
index 1cb2c84d00..0b76ab697f 100644
--- a/tests/Rust/tests/src/GuidTests.fs
+++ b/tests/Rust/tests/src/GuidTests.fs
@@ -49,6 +49,17 @@ let ``Guid.NewGuid works`` () =
     let g3 = Guid.Parse s1
     g1 = g3 |> equal true
 
+[<Fact>]
+let ``Guid.CreateVersion7 works`` () =
+    let g1 = Guid.CreateVersion7()
+    let g2 = Guid.CreateVersion7()
+    g1 = g2 |> equal false
+    let s1 = string g1
+    equal 36 s1.Length
+    equal '7' s1.[14]
+    let variantChar = s1.[19]
+    (variantChar = '8' || variantChar = '9' || variantChar = 'a' || variantChar = 'b') |> equal true
+
 // id is prefixed for guid creation as we check at compile time (if able) to create a string const
 [<Fact>]
 let ``Guid.Parse works`` () =

From 1d44d90a299b3dbbaaee9d4fb75939c63dbc6b75 Mon Sep 17 00:00:00 2001
From: Onur Gumus <onur@outlook.com.tr>
Date: Wed, 1 Apr 2026 16:30:35 +0200
Subject: [PATCH 2/8] Fix Rust Guid.CreateVersion7: use Timestamp::now instead
 of now_v7

---
 src/fable-library-rust/src/Guid.rs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/fable-library-rust/src/Guid.rs b/src/fable-library-rust/src/Guid.rs
index eca1af0547..08321a2788 100644
--- a/src/fable-library-rust/src/Guid.rs
+++ b/src/fable-library-rust/src/Guid.rs
@@ -54,7 +54,8 @@ pub mod Guid_ {
     }
 
     pub fn create_version7() -> Guid {
-        Guid(Uuid::now_v7())
+        let ts = uuid::Timestamp::now(uuid::NoContext);
+        Guid(Uuid::new_v7(ts))
     }
 
     pub fn create_version7_with_timestamp(dto: crate::DateTimeOffset_::DateTimeOffset) -> Guid {

From bc3c88a64d33bcabea6576e133ca4f7485b63e78 Mon Sep 17 00:00:00 2001
From: Onur Gumus <onur@outlook.com.tr>
Date: Wed, 1 Apr 2026 19:02:19 +0200
Subject: [PATCH 3/8] Simplify CreateVersion7 replacements: forward args
 directly

---
 src/Fable.Transforms/Beam/Replacements.fs   | 5 +----
 src/Fable.Transforms/Dart/Replacements.fs   | 7 ++-----
 src/Fable.Transforms/Python/Replacements.fs | 7 ++-----
 src/Fable.Transforms/Replacements.fs        | 7 ++-----
 4 files changed, 7 insertions(+), 19 deletions(-)

diff --git a/src/Fable.Transforms/Beam/Replacements.fs b/src/Fable.Transforms/Beam/Replacements.fs
index 7e08dc1891..d260ea022c 100644
--- a/src/Fable.Transforms/Beam/Replacements.fs
+++ b/src/Fable.Transforms/Beam/Replacements.fs
@@ -3855,10 +3855,7 @@ let private guids
             Helper.LibCall(com, "fable_guid", "from_bytes", t, [ arg ], ?loc = r) |> Some
         | _ -> None
     | "NewGuid" -> Helper.LibCall(com, "fable_guid", "new_guid", t, [], ?loc = r) |> Some
-    | "CreateVersion7" ->
-        match args with
-        | [] -> Helper.LibCall(com, "fable_guid", "create_version7", t, [], ?loc = r) |> Some
-        | _ -> Helper.LibCall(com, "fable_guid", "create_version7", t, args, ?loc = r) |> Some
+    | "CreateVersion7" -> Helper.LibCall(com, "fable_guid", "create_version7", t, args, ?loc = r) |> Some
     | "Parse" ->
         match args with
         | [ StringConst literalGuid ] ->
diff --git a/src/Fable.Transforms/Dart/Replacements.fs b/src/Fable.Transforms/Dart/Replacements.fs
index 9a8448239d..5f8dd6f1f0 100644
--- a/src/Fable.Transforms/Dart/Replacements.fs
+++ b/src/Fable.Transforms/Dart/Replacements.fs
@@ -3451,11 +3451,8 @@ let guids
     match i.CompiledName with
     | "NewGuid" -> Helper.LibCall(com, "Guid", "newGuid", t, []) |> Some
     | "CreateVersion7" ->
-        match args with
-        | [] -> Helper.LibCall(com, "Guid", "createVersion7", t, []) |> Some
-        | _ ->
-            Helper.LibCall(com, "Guid", "createVersion7", t, args, i.SignatureArgTypes)
-            |> Some
+        Helper.LibCall(com, "Guid", "createVersion7", t, args, i.SignatureArgTypes)
+        |> Some
     | "Parse" ->
         match args with
         | [ StringConst literalGuid ] -> parseGuid literalGuid
diff --git a/src/Fable.Transforms/Python/Replacements.fs b/src/Fable.Transforms/Python/Replacements.fs
index a1364a51b2..7f1f9215c4 100644
--- a/src/Fable.Transforms/Python/Replacements.fs
+++ b/src/Fable.Transforms/Python/Replacements.fs
@@ -3479,11 +3479,8 @@ let guids
     match i.CompiledName with
     | "NewGuid" -> Helper.LibCall(com, "guid", "new_guid", t, []) |> Some
     | "CreateVersion7" ->
-        match args with
-        | [] -> Helper.LibCall(com, "guid", "create_version7", t, []) |> Some
-        | _ ->
-            Helper.LibCall(com, "guid", "create_version7", t, args, i.SignatureArgTypes)
-            |> Some
+        Helper.LibCall(com, "guid", "create_version7", t, args, i.SignatureArgTypes)
+        |> Some
     | "Parse" -> Helper.LibCall(com, "guid", "parse", t, args, i.SignatureArgTypes) |> Some
     | "TryParse" -> Helper.LibCall(com, "guid", "try_parse", t, args, i.SignatureArgTypes) |> Some
     | "ToByteArray" ->
diff --git a/src/Fable.Transforms/Replacements.fs b/src/Fable.Transforms/Replacements.fs
index 55fb9aa4f8..0d82ed9084 100644
--- a/src/Fable.Transforms/Replacements.fs
+++ b/src/Fable.Transforms/Replacements.fs
@@ -3823,11 +3823,8 @@ let guids
     match i.CompiledName with
     | "NewGuid" -> Helper.LibCall(com, "Guid", "newGuid", t, []) |> Some
     | "CreateVersion7" ->
-        match args with
-        | [] -> Helper.LibCall(com, "Guid", "createVersion7", t, []) |> Some
-        | _ ->
-            Helper.LibCall(com, "Guid", "createVersion7", t, args, i.SignatureArgTypes)
-            |> Some
+        Helper.LibCall(com, "Guid", "createVersion7", t, args, i.SignatureArgTypes)
+        |> Some
     | "Parse" ->
         match args with
         | [ StringConst literalGuid ] -> parseGuid literalGuid

From 285d0c448b3b323cd3ff5ca45ed7975b21f1a33b Mon Sep 17 00:00:00 2001
From: ncave <777696+ncave@users.noreply.github.com>
Date: Wed, 1 Apr 2026 11:28:25 -0700
Subject: [PATCH 4/8] [Rust] Fix guid v7 impl

---
 src/fable-library-rust/Cargo.toml            |  4 ++--
 src/fable-library-rust/src/DateTimeOffset.rs |  4 ++++
 src/fable-library-rust/src/Guid.rs           | 16 ++++++++--------
 3 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/src/fable-library-rust/Cargo.toml b/src/fable-library-rust/Cargo.toml
index 1f738b2508..0244c55b69 100644
--- a/src/fable-library-rust/Cargo.toml
+++ b/src/fable-library-rust/Cargo.toml
@@ -31,7 +31,7 @@ rust_decimal = { version = "1.40", features = ["maths"], default-features = fals
 startup = { version = "0.1", path = "vendored/startup", optional = true }
 
 [target.'cfg(not(target_arch = "wasm32"))'.dependencies]
-uuid = { version = "1.22", features = ["v4", "v7"], default-features = false, optional = true }
+uuid = { version = "1.23", features = ["v4", "v7"], default-features = false, optional = true }
 
 [target.'cfg(target_arch = "wasm32")'.dependencies]
-uuid = { version = "1.22", features = ["v4", "v7", "js"], default-features = false, optional = true }
+uuid = { version = "1.23", features = ["v4", "v7", "js"], default-features = false, optional = true }
diff --git a/src/fable-library-rust/src/DateTimeOffset.rs b/src/fable-library-rust/src/DateTimeOffset.rs
index 419058d622..9f3ce85de5 100644
--- a/src/fable-library-rust/src/DateTimeOffset.rs
+++ b/src/fable-library-rust/src/DateTimeOffset.rs
@@ -277,6 +277,10 @@ pub mod DateTimeOffset_ {
             self.0.timestamp()
         }
 
+        pub fn toUnixTimeSubsecNanos(&self) -> u32 {
+            self.0.timestamp_subsec_nanos()
+        }
+
         pub fn year(&self) -> i32 {
             self.0.year()
         }
diff --git a/src/fable-library-rust/src/Guid.rs b/src/fable-library-rust/src/Guid.rs
index 08321a2788..4037b7d3c1 100644
--- a/src/fable-library-rust/src/Guid.rs
+++ b/src/fable-library-rust/src/Guid.rs
@@ -1,9 +1,10 @@
 #[cfg(feature = "guid")]
 pub mod Guid_ {
+    use crate::DateTimeOffset_::DateTimeOffset;
     use crate::NativeArray_::{new_array, Array};
     use crate::Native_::{compare, MutCell};
     use crate::String_::{string, toString};
-    use uuid::Uuid;
+    use uuid::{NoContext, Timestamp, Uuid};
 
     #[derive(Clone, Copy, Debug, Default, PartialEq, PartialOrd)]
     pub struct Guid(Uuid);
@@ -54,15 +55,14 @@ pub mod Guid_ {
     }
 
     pub fn create_version7() -> Guid {
-        let ts = uuid::Timestamp::now(uuid::NoContext);
-        Guid(Uuid::new_v7(ts))
+        let dto = DateTimeOffset::utcNow();
+        create_version7_with_timestamp(dto)
     }
 
-    pub fn create_version7_with_timestamp(dto: crate::DateTimeOffset_::DateTimeOffset) -> Guid {
-        let millis = dto.toUnixTimeMilliseconds();
-        let secs = (millis / 1000) as u64;
-        let nanos = ((millis % 1000) * 1_000_000) as u32;
-        let ts = uuid::Timestamp::from_unix(uuid::NoContext, secs, nanos);
+    pub fn create_version7_with_timestamp(dto: DateTimeOffset) -> Guid {
+        let seconds = dto.toUnixTimeSeconds() as u64;
+        let subsec_nanos = dto.toUnixTimeSubsecNanos();
+        let ts = Timestamp::from_unix(NoContext, seconds, subsec_nanos);
         Guid(Uuid::new_v7(ts))
     }
 }

From b27bd28701c9bb3db58bad7f53f16e20ac6ac172 Mon Sep 17 00:00:00 2001
From: ncave <777696+ncave@users.noreply.github.com>
Date: Wed, 1 Apr 2026 17:41:14 -0700
Subject: [PATCH 5/8] Test guids v7 are monotonic

---
 src/Fable.Cli/CHANGELOG.md                    |  1 +
 src/Fable.Compiler/CHANGELOG.md               |  1 +
 .../fable_library/date_offset.py              | 12 +++++++++-
 tests/Beam/DateTimeOffsetTests.fs             |  2 ++
 tests/Beam/GuidTests.fs                       | 18 ++++++++++----
 tests/Js/Main/TypeTests.fs                    | 17 +++++++++----
 tests/Python/TestDateTimeOffset.fs            |  2 ++
 tests/Python/TestGuid.fs                      | 18 ++++++++++----
 tests/Rust/tests/src/GuidTests.fs             | 24 +++++++++++++++++--
 9 files changed, 80 insertions(+), 15 deletions(-)

diff --git a/src/Fable.Cli/CHANGELOG.md b/src/Fable.Cli/CHANGELOG.md
index 0748f399aa..7f577100c9 100644
--- a/src/Fable.Cli/CHANGELOG.md
+++ b/src/Fable.Cli/CHANGELOG.md
@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
+* [Python] Fix `DateTimeOffset` millisecond constructor and property (by @ncave)
 * [All] Add support for `Guid.CreateVersion7()` and `Guid.CreateVersion7(DateTimeOffset)`
 
 ## 5.0.0-rc.6 - 2026-03-31
diff --git a/src/Fable.Compiler/CHANGELOG.md b/src/Fable.Compiler/CHANGELOG.md
index e916128cd5..8ac54fe7f6 100644
--- a/src/Fable.Compiler/CHANGELOG.md
+++ b/src/Fable.Compiler/CHANGELOG.md
@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
+* [Python] Fix `DateTimeOffset` millisecond constructor and property (by @ncave)
 * [All] Add support for `Guid.CreateVersion7()` and `Guid.CreateVersion7(DateTimeOffset)`
 
 ## 5.0.0-rc.12 - 2026-03-31
diff --git a/src/fable-library-py/fable_library/date_offset.py b/src/fable-library-py/fable_library/date_offset.py
index 22dbd0285c..a06c4219f2 100644
--- a/src/fable-library-py/fable_library/date_offset.py
+++ b/src/fable-library-py/fable_library/date_offset.py
@@ -149,7 +149,7 @@ def create(
         ms = 0
 
     if python_offset is None:
-        dt = datetime(year, month, day, h, m, s, ms)
+        dt = datetime(year, month, day, h, m, s, ms * 1000)
         if offset is not None:
             offset_ms = int(time_span.total_microseconds(offset) / 1000)
             python_offset = timedelta(microseconds=float(time_span.total_microseconds(offset)))
@@ -207,6 +207,14 @@ def second(d: DateTimeOffset) -> int:
     return d.second
 
 
+def millisecond(d: DateTimeOffset) -> int:
+    return d.microsecond // 1000
+
+
+def microsecond(d: DateTimeOffset) -> int:
+    return d.microsecond % 1000
+
+
 def op_subtraction(x: DateTimeOffset, y: DateTimeOffset | TimeSpan) -> DateTimeOffset | TimeSpan:
     if isinstance(y, TimeSpan):
         # Subtract TimeSpan from DateTimeOffset
@@ -231,6 +239,8 @@ def op_subtraction(x: DateTimeOffset, y: DateTimeOffset | TimeSpan) -> DateTimeO
     "op_subtraction",
     "parse",
     "second",
+    "millisecond",
+    "microsecond",
     "try_parse",
     "utc_now",
     "year",
diff --git a/tests/Beam/DateTimeOffsetTests.fs b/tests/Beam/DateTimeOffsetTests.fs
index a0fe1da132..ae5d2cdd5f 100644
--- a/tests/Beam/DateTimeOffsetTests.fs
+++ b/tests/Beam/DateTimeOffsetTests.fs
@@ -35,6 +35,8 @@ let ``test DateTimeOffset constructors work`` () =
     d.Hour |> equal 13
     d.Minute |> equal 23
     d.Second |> equal 30
+    let d2 = DateTimeOffset(2014, 10, 9, 13, 23, 30, 500, TimeSpan.Zero)
+    d2.Second + d2.Millisecond |> equal 530
 
 [<Fact>]
 let ``test DateTimeOffset.Offset works`` () =
diff --git a/tests/Beam/GuidTests.fs b/tests/Beam/GuidTests.fs
index f0eccab334..bdcb9c09e2 100644
--- a/tests/Beam/GuidTests.fs
+++ b/tests/Beam/GuidTests.fs
@@ -28,20 +28,30 @@ let ``test Guid.CreateVersion7 works`` () =
     g1 = g2 |> equal false
     let s1 = string g1
     equal 36 s1.Length
-    equal '7' s1.[14]
-    let variantChar = s1.[19]
+    equal '7' s1[14]
+    let variantChar = s1[19]
     (variantChar = '8' || variantChar = '9' || variantChar = 'a' || variantChar = 'b') |> equal true
 
 [<Fact>]
 let ``test Guid.CreateVersion7 with DateTimeOffset works`` () =
     let dto = DateTimeOffset(2024, 1, 1, 0, 0, 0, TimeSpan.Zero)
     let g1 = Guid.CreateVersion7(dto)
+    let g2 = Guid.CreateVersion7(dto)
+    g1 = g2 |> equal false
     let s1 = string g1
     equal 36 s1.Length
-    equal '7' s1.[14]
-    let variantChar = s1.[19]
+    equal '7' s1[14]
+    let variantChar = s1[19]
     (variantChar = '8' || variantChar = '9' || variantChar = 'a' || variantChar = 'b') |> equal true
 
+[<Fact>]
+let ``test Guid.CreateVersion7 is monotonic`` () =
+    [1 .. 100]
+    |> List.map (fun ms -> DateTimeOffset(2024, 1, 1, 0, 0, 0, ms, TimeSpan.Zero))
+    |> List.map (fun dto -> Guid.CreateVersion7(dto))
+    |> List.pairwise
+    |> List.iter (fun (g1, g2) -> g1 < g2 |> equal true)
+
 [<Fact>]
 let ``test Guid equality works`` () =
     let s = "f46d24f0-183e-4fca-9f47-e382afdfde8b"
diff --git a/tests/Js/Main/TypeTests.fs b/tests/Js/Main/TypeTests.fs
index 2435ef4534..986d434c15 100644
--- a/tests/Js/Main/TypeTests.fs
+++ b/tests/Js/Main/TypeTests.fs
@@ -1126,20 +1126,29 @@ let tests =
         let s1 = string g1
         equal 36 s1.Length
         // Check version nibble is '7'
-        equal '7' s1.[14]
+        equal '7' s1[14]
         // Check variant nibble is 8, 9, a, or b
-        let variantChar = s1.[19]
+        let variantChar = s1[19]
         (variantChar = '8' || variantChar = '9' || variantChar = 'a' || variantChar = 'b') |> equal true
 
     testCase "Guid.CreateVersion7 with DateTimeOffset works" <| fun () ->
         let dto = DateTimeOffset(2024, 1, 1, 0, 0, 0, TimeSpan.Zero)
         let g1 = Guid.CreateVersion7(dto)
+        let g2 = Guid.CreateVersion7(dto)
+        g1 = g2 |> equal false
         let s1 = string g1
         equal 36 s1.Length
-        equal '7' s1.[14]
-        let variantChar = s1.[19]
+        equal '7' s1[14]
+        let variantChar = s1[19]
         (variantChar = '8' || variantChar = '9' || variantChar = 'a' || variantChar = 'b') |> equal true
 
+    testCase "Guid.CreateVersion7 is monotonic" <| fun () ->
+        [1 .. 100]
+        |> List.map (fun ms -> DateTimeOffset(2024, 1, 1, 0, 0, 0, ms, TimeSpan.Zero))
+        |> List.map (fun dto -> Guid.CreateVersion7(dto))
+        |> List.pairwise
+        |> List.iter (fun (g1, g2) -> g1 < g2 |> equal true)
+
     testCase "Guid.Empty works" <| fun () ->
         let g1 = Guid.Empty
         string g1 |> equal "00000000-0000-0000-0000-000000000000"
diff --git a/tests/Python/TestDateTimeOffset.fs b/tests/Python/TestDateTimeOffset.fs
index 8e39fe878c..59a59b3394 100644
--- a/tests/Python/TestDateTimeOffset.fs
+++ b/tests/Python/TestDateTimeOffset.fs
@@ -37,6 +37,8 @@ let ``test DateTimeOffset constructors work`` () =
     d.Hour |> equal 13
     d.Minute |> equal 23
     d.Second |> equal 30
+    let d2 = DateTimeOffset(2014, 10, 9, 13, 23, 30, 500, TimeSpan.Zero)
+    d2.Second + d2.Millisecond |> equal 530
 
 [<Fact>]
 let ``test DateTimeOffset.Offset works`` () =
diff --git a/tests/Python/TestGuid.fs b/tests/Python/TestGuid.fs
index bb5cc843a3..04cf7aad89 100644
--- a/tests/Python/TestGuid.fs
+++ b/tests/Python/TestGuid.fs
@@ -28,20 +28,30 @@ let ``test Guid.CreateVersion7 works`` () =
     g1 = g2 |> equal false
     let s1 = string g1
     equal 36 s1.Length
-    equal '7' s1.[14]
-    let variantChar = s1.[19]
+    equal '7' s1[14]
+    let variantChar = s1[19]
     (variantChar = '8' || variantChar = '9' || variantChar = 'a' || variantChar = 'b') |> equal true
 
 [<Fact>]
 let ``test Guid.CreateVersion7 with DateTimeOffset works`` () =
     let dto = DateTimeOffset(2024, 1, 1, 0, 0, 0, TimeSpan.Zero)
     let g1 = Guid.CreateVersion7(dto)
+    let g2 = Guid.CreateVersion7(dto)
+    g1 = g2 |> equal false
     let s1 = string g1
     equal 36 s1.Length
-    equal '7' s1.[14]
-    let variantChar = s1.[19]
+    equal '7' s1[14]
+    let variantChar = s1[19]
     (variantChar = '8' || variantChar = '9' || variantChar = 'a' || variantChar = 'b') |> equal true
 
+[<Fact>]
+let ``test Guid.CreateVersion7 is monotonic`` () =
+    [1 .. 100]
+    |> List.map (fun ms -> DateTimeOffset(2024, 1, 1, 0, 0, 0, ms, TimeSpan.Zero))
+    |> List.map (fun dto -> Guid.CreateVersion7(dto))
+    |> List.pairwise
+    |> List.iter (fun (g1, g2) -> g1 < g2 |> equal true)
+
 [<Fact>]
 let ``test Guid equality works`` () =
     let s = "f46d24f0-183e-4fca-9f47-e382afdfde8b"
diff --git a/tests/Rust/tests/src/GuidTests.fs b/tests/Rust/tests/src/GuidTests.fs
index 0b76ab697f..976b9267bf 100644
--- a/tests/Rust/tests/src/GuidTests.fs
+++ b/tests/Rust/tests/src/GuidTests.fs
@@ -56,10 +56,30 @@ let ``Guid.CreateVersion7 works`` () =
     g1 = g2 |> equal false
     let s1 = string g1
     equal 36 s1.Length
-    equal '7' s1.[14]
-    let variantChar = s1.[19]
+    equal '7' s1[14]
+    let variantChar = s1[19]
     (variantChar = '8' || variantChar = '9' || variantChar = 'a' || variantChar = 'b') |> equal true
 
+[<Fact>]
+let ``Guid.CreateVersion7 with DateTimeOffset works`` () =
+    let dto = DateTimeOffset(2024, 1, 1, 0, 0, 0, TimeSpan.Zero)
+    let g1 = Guid.CreateVersion7(dto)
+    let g2 = Guid.CreateVersion7(dto)
+    g1 = g2 |> equal false
+    let s1 = string g1
+    equal 36 s1.Length
+    equal '7' s1[14]
+    let variantChar = s1[19]
+    (variantChar = '8' || variantChar = '9' || variantChar = 'a' || variantChar = 'b') |> equal true
+
+[<Fact>]
+let ``Guid.CreateVersion7 with DateTimeOffset is monotonic`` () =
+    [1 .. 100]
+    |> List.map (fun ms -> DateTimeOffset(2024, 1, 1, 0, 0, 0, ms, TimeSpan.Zero))
+    |> List.map (fun dto -> Guid.CreateVersion7(dto))
+    |> List.pairwise
+    |> List.iter (fun (g1, g2) -> g1 < g2 |> equal true)
+
 // id is prefixed for guid creation as we check at compile time (if able) to create a string const
 [<Fact>]
 let ``Guid.Parse works`` () =

From 5ea70116b9bedc3301a37429aa038e8c7d02b2d0 Mon Sep 17 00:00:00 2001
From: ncave <777696+ncave@users.noreply.github.com>
Date: Thu, 2 Apr 2026 00:43:53 -0700
Subject: [PATCH 6/8] Code review fixes

---
 src/fable-library-py/fable_library/guid.py | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/src/fable-library-py/fable_library/guid.py b/src/fable-library-py/fable_library/guid.py
index ffe1c95605..da5b07391b 100644
--- a/src/fable-library-py/fable_library/guid.py
+++ b/src/fable-library-py/fable_library/guid.py
@@ -1,9 +1,10 @@
-import os
+import secrets
 import time
 import uuid
 
 from .array_ import Array
 from .core import FSharpRef, byte
+from .date_offset import DateTimeOffset
 
 
 def parse(string: str) -> uuid.UUID:
@@ -34,7 +35,7 @@ def array_to_guid(guid: Array[byte]) -> uuid.UUID:
     return uuid.UUID(bytes_le=bytes(guid))
 
 
-def create_version7(timestamp: object | None = None) -> uuid.UUID:
+def create_version7(timestamp: DateTimeOffset | None = None) -> uuid.UUID:
     """Create a UUID v7 per RFC 9562."""
     if timestamp is None:
         ms = int(time.time() * 1000)
@@ -43,7 +44,7 @@ def create_version7(timestamp: object | None = None) -> uuid.UUID:
         ms = int(timestamp.getTime())  # type: ignore
 
     # Build 16 bytes per RFC 9562
-    rand_bytes = os.urandom(10)
+    rand_bytes = secrets.token_bytes(10)
 
     # Bytes 0-5: 48-bit big-endian ms timestamp
     ts_bytes = ms.to_bytes(6, byteorder="big")

From b5fdcdcd224c99d4274eeb9649fbd60d8cd866ac Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=D0=A1=D0=BB=D0=B0=D0=B2=D0=B0=20=D0=A3=D0=BA=D1=80=D0=B0?=
 =?UTF-8?q?=D1=97=D0=BD=D1=96!=20=D0=93=D0=B5=D1=80=D0=BE=D1=8F=D0=BC=20?=
 =?UTF-8?q?=D1=81=D0=BB=D0=B0=D0=B2=D0=B0!?=
 <777696+ncave@users.noreply.github.com>
Date: Thu, 2 Apr 2026 02:35:43 -0700
Subject: [PATCH 7/8] Update src/fable-library-py/fable_library/guid.py

Co-authored-by: Dag Brattli <dag@brattli.net>
---
 src/fable-library-py/fable_library/guid.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/fable-library-py/fable_library/guid.py b/src/fable-library-py/fable_library/guid.py
index da5b07391b..114d12c21d 100644
--- a/src/fable-library-py/fable_library/guid.py
+++ b/src/fable-library-py/fable_library/guid.py
@@ -41,7 +41,7 @@ def create_version7(timestamp: DateTimeOffset | None = None) -> uuid.UUID:
         ms = int(time.time() * 1000)
     else:
         # DateTimeOffset has getTime() returning ms since epoch
-        ms = int(timestamp.getTime())  # type: ignore
+        ms = int(timestamp.getTime())
 
     # Build 16 bytes per RFC 9562
     rand_bytes = secrets.token_bytes(10)

From 6bce8f952bdde8dd59e95fd992aa2bf36a6cc02b Mon Sep 17 00:00:00 2001
From: ncave <777696+ncave@users.noreply.github.com>
Date: Thu, 2 Apr 2026 03:23:07 -0700
Subject: [PATCH 8/8] [JS/TS] Fix `Guid` to use cryptographically strong random
 values

---
 src/Fable.Cli/CHANGELOG.md      |  4 +++-
 src/Fable.Compiler/CHANGELOG.md |  4 +++-
 src/fable-library-ts/Guid.ts    | 25 +++++++++++++------------
 3 files changed, 19 insertions(+), 14 deletions(-)

diff --git a/src/Fable.Cli/CHANGELOG.md b/src/Fable.Cli/CHANGELOG.md
index d1482782dd..ce1258499b 100644
--- a/src/Fable.Cli/CHANGELOG.md
+++ b/src/Fable.Cli/CHANGELOG.md
@@ -9,10 +9,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
-* [Python] Fix `DateTimeOffset` millisecond constructor and property (by @ncave)
 * [All] Add support for `Guid.CreateVersion7()` and `Guid.CreateVersion7(DateTimeOffset)`
+
 ### Fixed
 
+* [JS/TS] Fix `Guid` to use cryptographically strong random values (by @ncave)
+* [Python] Fix `DateTimeOffset` millisecond constructor and property (by @ncave)
 * [Python] Fix `String.IndexOf`/`LastIndexOf` with `StringComparison` argument emitting it as a start-index instead of a compile error (by @repo-assist)
 * [Beam] Fix `String.IndexOf`/`LastIndexOf` with `StringComparison` argument incorrectly treating the enum value as a start index
 
diff --git a/src/Fable.Compiler/CHANGELOG.md b/src/Fable.Compiler/CHANGELOG.md
index 81d85a92d8..1fe7753e52 100644
--- a/src/Fable.Compiler/CHANGELOG.md
+++ b/src/Fable.Compiler/CHANGELOG.md
@@ -9,10 +9,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
-* [Python] Fix `DateTimeOffset` millisecond constructor and property (by @ncave)
 * [All] Add support for `Guid.CreateVersion7()` and `Guid.CreateVersion7(DateTimeOffset)`
+
 ### Fixed
 
+* [JS/TS] Fix `Guid` to use cryptographically strong random values (by @ncave)
+* [Python] Fix `DateTimeOffset` millisecond constructor and property (by @ncave)
 * [Python] Fix `String.IndexOf`/`LastIndexOf` with `StringComparison` argument emitting it as a start-index instead of a compile error (by @repo-assist)
 * [Beam] Fix `String.IndexOf`/`LastIndexOf` with `StringComparison` argument incorrectly treating the enum value as a start index
 
diff --git a/src/fable-library-ts/Guid.ts b/src/fable-library-ts/Guid.ts
index 5bf7f31e78..e74d2011a0 100644
--- a/src/fable-library-ts/Guid.ts
+++ b/src/fable-library-ts/Guid.ts
@@ -63,15 +63,13 @@ export function tryParse(str: string, defValue: FSharpRef<string>): boolean {
   }
 }
 
-// From https://gist.github.com/LeverOne/1308368
 export function newGuid() {
-  let b = "";
-  for (let a = 0; a++ < 36;) {
-    b += a * 51 & 52
-      ? (a ^ 15 ? 8 ^ Math.random() * (a ^ 20 ? 16 : 4) : 4).toString(16)
-      : "-";
-  }
-  return b;
+  const bytes = new Uint8Array(16);
+  crypto.getRandomValues(bytes);
+  bytes[6] = (bytes[6] & 0x0f) | 0x40; // version 4
+  bytes[8] = (bytes[8] & 0x3f) | 0x80; // variant 1
+  const hex = Array.from(bytes, b => b.toString(16).padStart(2, "0")).join("");
+  return `${hex.slice(0, 8)}-${hex.slice(8, 12)}-${hex.slice(12, 16)}-${hex.slice(16, 20)}-${hex.slice(20)}`;
 }
 
 // RFC 9562 UUID v7
@@ -82,10 +80,13 @@ export function createVersion7(timestamp?: Date): string {
   const msHex = Math.floor(ms).toString(16).padStart(12, "0");
 
   // random bits
-  const randA = Math.floor(Math.random() * 0x1000); // 12 bits
-  const randB1 = Math.floor(Math.random() * 0x4000); // 14 bits
-  const randB2 = Math.floor(Math.random() * 0x100000000); // 32 bits
-  const randB3 = Math.floor(Math.random() * 0x10000); // 16 bits
+  const bytes = new Uint8Array(10);
+  crypto.getRandomValues(bytes);
+  const view = new DataView(bytes.buffer);
+  const randA = view.getUint16(0) & 0x0fff; // 12 bits
+  const randB1 = view.getUint16(2) & 0x3fff; // 14 bits
+  const randB2 = view.getUint32(4); // 32 bits
+  const randB3 = view.getUint16(8); // 16 bits
 
   const timeLow = msHex.slice(0, 8);
   const timeMid = msHex.slice(8, 12);